Mood disorders are generally classified by type and include, but are not limited to:
A morbid or clinical depression, which is usually diagnosed when sadness or elation is overly intense and continues beyond the expected impact of an event. Symptoms often recur on an episodic basis or pursue a low-grade intermittent chronicity, which impairs the functioning of the sufferer.
Bipolar mood disorder, which commonly begins with depression and is characterised by periods of elation during the course of the illness.
Unipolar mood disorder, which is characterised as syndromal depression of episodes that last for typically 6 to 9 months.
The pharmaceuticals used in the treatment of Bipolar mood disorders can be grouped into three classes; the heterocyclic antidepressants (HCAs), monoamine oxidase inhibitors (MAOIs) and lithium salts.
HCAs are the largest class of antidepressants and include tricyclic antidepressants such as imipramine. The HCAs have no immediate effect on euphoria and therefore have a low abuse potential. This group of antidepressants work by increasing the availability of the biogenic amines norepinephrine and/or serotonin (5-HT) by blocking reuptake in the synaptic cleft. The side effects of HCAs include tachycardia, postural hypotension and cardio-toxicity. HCAs are also commonly associated with blurred vision, xerostomia, constipation, urinary hesitation, sedation and weight gain. The hypotensive side effects of HCAs often make them unsuitable for patients with mental disorders and the elderly.
MAOIs such as phenelzine are often prescribed for panic disorders. They work by the inhibition of the oxidative deamination of the 3 classes of biogenic amines; noradrenergic, dopaminergic and 5-HT. MAOIs are underused because of clinician's fears of hypertension that may result from dietary or drug reactions, popularly known as the ‘cheese reaction’ due to the high tyramine content in cheeses and other foods. Other common side effects of MAOIs include erectile difficulties, anxiety, nausea, dizziness, insomnia, edema and weight gain.
Lithium is used to stabilise the often unpredictable mood swings in bipolar mood disorder. The precise mechanism of action is unknown, but it is postulated that it is able to cause hyperpolarisation of the neuronal membrane. The most common acute benign side effects are tremour, fasciculation, nausea, diarrhoea, polyuria, polydipsia and weight gain. Lithium toxicity is more likely in elderly patients.
The applicants have previously shown that the cannabinoid cannabichromene is useful in the treatment of mood disorders as described in the International patent application WO2005/000830. However the actions of many cannabinoids such as THC are linked with an increase in mood disorders in users.